In a motor vehicle a suspension generally supports the vehicle frame in a position above the suspension components. When a suspension component fails, support for the frame may be lost, and the frame "bottoms out" whereupon the frame falls down upon lower vehicle components such as axle housings, differentials, or tires and wheels. It is known to use a metal stop positioned between the frame and axle housing to stop over travel of the suspension or to absorb impact between the frame and axle housing if the suspension fails. The metal stop also serves to prevent total collapse of the frame upon other lower vehicle components and suspension components.
The known metal stops might prevent total collapse of the frame upon lower suspension components if the vehicle were stationary. However, when a failure of suspension components occurs as the vehicle is in motion, another serious and potentially disastrous problem may occur. The major vehicle components that are located beneath a frame and that are first contacted when a suspension failure occurs are the stop block and axle housing. During motion of the vehicle, the wheels are spinning, and when the body collapses upon the spinning wheels the body serves as a brake upon the spinning wheels to cause their motion to be slowed down severely. In spite of the fact that the wheels are slowed down, the body and the load that is borne by the body continue to have considerable momentum in the direction of motion. As a result, the unsupported portion of the body above the wheels tends to continue forward and be translated forward with respect to the wheels. In the brief matter of seconds or less, the frame and body can translate so that the wheels move out from under the suspension stop. At this point the frame, no longer supported by the wheels or the axle stop allows the walking beam to come into contact with the road surface which causes vehicle rollover or loss of control.
Furthermore, if a suspension failure occurs on only one side of the rear of the vehicle with the suspension on the other side of the vehicle remaining intact, the axle and wheels will translate in a skewed manner causing the wheels to exert unwanted steering forces on the vehicle creating dangerous conditions resulting in complete loss of control.
Furthermore, the experience of the present inventor has shown that even at a low speed of about 10 miles per hour (16 kilometers per hour), failure of a walking beam sleeve or other related suspension components can cause the vehicle to overturn. Drivers and passengers have been killed or injured in such accidents.
In case of a vehicle roll over, in addition to requiring costly repair of failed suspension components, there would be excessive costs for repair of additional vehicle components damaged during the roll over not to mention personal injury and loss of life.
More specifically, the following failure sequence may occur on either side or front or back of a vehicle equipped with a walking beam suspension. First, the walking beam or another suspension component fails as the vehicle is moving. Then, a frame rail, released from its support by the suspension due to the failure, falls along with the vehicle body supported thereby. The vehicle body then strikes the tires which may shred and blow out because they are cut by underbody parts. However, the unsupported vehicle body and frame continue on their forward motion thereby causing the vehicle body and frame to translate and move away from the axle. Once the vehicle body causes tire failure the whole vehicle will lean excessively to one side, and roll over and/or loss of control will then occur.
Another manner of failure of a walking beam suspension can also occur. If the forward end of the walking beam fails, the walking beam can dig into the road surface and catapult the side of the vehicle upward, turning it on its side or overturning it completely depending on the vehicle speed and the surface that is travelled.
Suspension failure can occur when the vehicle is moving either forward or in the reverse direction.
Another problem associated with a suspension failure described above is that the natural reaction of a driver would be to apply the brakes during the failure. However, application of the brakes has a deleterious effect in that it increases the tendency of the failed suspension to separate from the vehicle.
Still another problem associated with a suspension failure may be the reaction of a vehicle operator to apply more throttle in the event of a suspension failure. In such a case, the axle housing would translate forward in relation to the frame causing the suspension stop to slip off the rear of the axle housing. Thereby, the frame and body would similarly lean excessively.